80 minutes

Before beginning this lesson, students can identify the five senses and corresponding organs. They understand the nervous system is responsible for recieving, analyzing and sending messages throughout the body.

• The sensory neurons carry impulses from the sense organs back to the central nervous system
• The largest sense organ in the body is the skin, which contains different receptors for touch, pain, heat and cold.
• These receptors are not equally distributed over the skin, which causes certain parts of the body to be more sensitive than others.

• Students understand that sensory neurons are responsible for relaying information from the sense organs to the central nervous system for analysis.
• Students investigate the distribution of touch receptors in the skin
• Students recognize the relationship between the density of receptors and sensitivity

• Toothpicks (9 per group)
  • Single
  • Two taped together 5mm apart
  • Two taped together 10mm apart
  • Two taped together 15mm apart
  • Two taped together 20mm apart
• Duct Tape

Procedure

Opener
1. As a DO NOW activity, the students identify the five senses and corresponding organ.

Development
1. Instructor presents new material: A more detalied discussion of the 5 senses outlining the specific sensory neurons used in each process.
2. In groups of two, the students investigate the distribution of touch receptors in the skin following the procedure outlined in the handout.

Closure
1. As students finish exercise, they enter their groups data into a class data table in the board.
2. A class average is generated to determine the most sensitive part and least sensitive part tested.

Students are required to complete a data chart tracking the responses of each group member to the different stimuli. Additionally, there are three analysis questions to be answered on the handout.

Biology: The Living Science. Prentice Hall (1998).
(Text Book and Lab Manual)